Publication Date:
2015-12-25
Description:
We performed extensive tests of the accuracy of atmospheric parameter determination for FGK stars based on the spectrum fitting procedure Spectroscopy Made Easy ( sme ). Our stellar sample consists of 13 objects, including the Sun, in the temperature range 5000–6600 K and metallicity range –1.4–+0.4. The analysed stars have the advantage of having parameters derived by interferometry. For each star, we use spectra obtained with different spectrographs and different signal-to-noise ratios (S/N). For the fitting, we adopted three different sets of constraints and test how the derived parameters depend upon the spectral regions (masks) used in sme . We developed and implemented in sme a new method for estimating uncertainties in the resulting parameters based on fitting residuals, partial derivatives, and data uncertainties. For stars in the 5700–6600 K range, the best agreement with the effective temperatures derived by interferometry is achieved when spectrum fitting includes the H α and H β lines, while for cooler stars the choice of the mask does not affect the results. The derived atmospheric parameters do not strongly depend on spectral resolution and S/N of the observations, while the uncertainties in temperature and surface gravity increase with increasing effective temperature, with minima at 50 K in T eff and 0.1 dex in log g , for spectra with S/N=150–200. A non-local thermodynamic equilibrium (NLTE) analysis of the Ti i /Ti ii and Fe i /Fe ii ionization equilibria and abundances determined from the atomic C i (NLTE) and molecular CH species supports the parameters we derived with sme by fitting the observed spectra including the hydrogen lines.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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